Novel damping compositions

ABSTRACT

A process of using compositions comprising certain thermoplastic elastomeric polymers for damping and damping compositions comprising soft thermoset polymer containing microscopically discrete segments of said thermoplastic elastomeric polymers.

This is a divisional of application Ser. No. 336,187, filed Apr. 11,1989 now U.S. Pat. No. 5,008,324.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the use of a certain multi-phase,thermoplastic elastomeric polymer for damping purposes, and new dampingcompositions comprising said polymer.

2. Description of the Prior Art

Lorentz et al., pps. 306-329, in Piirma and Gardon, ed., "EmulsionPolymerization", American Chemical Society Symposium Series 24,Washington, DC, 1976, and Sperling, pps. 21-56, Paul and Sperling, ed.,"Multicomponent Polymeric Materials", American Chemical SocietySymposium Series 211, Washington, D.C., 1986, have discussed in detailthe damping properties of two-phase emulsion polymers of varyingcomposition wherein the second polymer is polymerized in the presence ofthe first.

Lohr, U.S. Pat. No. 3,430,902 teaches a vibration damping devicecomprising a solid, high molecular weight amorphous polymer utilized ator near its glass temperature combined with means for heating or coolingso that the glass temperature is approximately that of the usetemperature of the vibration support.

Tabar et al. U.S. Pat. No. 4,362,840 and U.S. Pat. No. 4,419,480;Lemieux et al., Rubber Chem. Tech., 57, 792 (1984); Mazich et al. ibid.,59, 623 (1986) teach soft compositions useful as low modulus, highdamping, high fatigue life elastomer compounds for vibration isolation.The compounds are cured, vulcanized, or crosslinked blends of naturalrubber with bromobutyl rubber to which has been added a non-vulcanizablepolyisobutylene which remains in a discrete phase after cure; aparticulate additive such as carbon black is also incorporated. Thesetwo patents also teach the use of synthetic poly(isoprene) orpolybutadiene in similar blends to improve the heat resistance of theblend.

Falk et al, U.S. Pat. No. 4,473,679, claim thermoplastic core-shellcompositions having a rigid core surrounded by a rubbery acrylicpartially encapsulating layer, with a copolymeric transition layerformed from the mixture of monomers used to prepare the core and shelllayer.

Makati et al, U.S. Pat. No. 4,717,750 and U.S. Pat. No. 4,742,108; Leeet al., U.S. Pat. No. 4,569,964 teach reinforced latex particlestructures. The Makati et al. patents teach a second phase of glasstemperature higher than either the first or third phase.

Hofmann, U.S. Pat. No. 4,180,529, teaches a four-phased emulsion polymerhaving a non-elastomeric second phase which may contain up to 5% of acrosslinking monomer in combination with a elastomeric first phase.Owens, U.S. Pat. No. 3,793,402 teaches a similar staging with anadditional thermoplastic outer phase.

The Derwent abstract of Japanese Patent 79-8497 teaches blends of liquidthermosetting resins with rubbery polymers and linear thermoplasticresins as vibration-reducing materials useful at high temperatures andflexible at ordinary temperature.

The Derwent abstract of Japanese Patent 88-1979 teaches blends ofnatural rubber with a soluble chloromethylstyrene-butadiene-styreneterpolymer as a useful high modulus elastomeric product.

Frankel et al. European Patent Application 187,505, published July 16,1986, teach two-phase polymers used in the present invention.

Sugii et al. (Nitto Electric) in Japanese Kokai 60-92372 teach a polymeruseful as an improved pressure sensitive adhesive by first polymerizinga (meth)acrylic polymer which produces a tacky material, adding amonomer mixture enriched in a multifunctional monomer, along with anorganic peroxide, to swell the particles and conducting thepolymerization of the second monomers at an elevated temperature.

SUMMARY OF THE INVENTION

The present invention is directed to a process which comprises using acertain multi-phase thermoplastic elastomeric polymer for damping, i.e.,as a damping material. The multi-phase polymer has at least twopolymeric phases: (a) an initial (i.e. first) linear or lightlycrosslinked polymeric phase polymerized from an α, β ethylenicallyunsaturated monomer, wherein the α, β ethylenically unsaturated monomercomprises from about 0 to about 2% by weight of multi-ethylenicallyunsaturated monomer, and (b) a second polymeric phase in the form ofdiscrete domains of about 2 to about 15 nm in diameter dispersed withinthe initial polymeric phase, wherein the second polymeric phase ispolymerized from at least one ethylenically unsaturated monomercomprised of about 5% to 100% by weight multifunctional monomer havingat least two sites of ethylenic unsaturation. The weight ratio of thesecond polymeric phase to the initial polymeric phase plus said secondpolymeric phase is from about 1:100 to about 1:2. The multi-phasepolymer may further comprise a final (i.e., third) polymericthermoplastic phase whose glass transition temperature is greater thanthat of the initial polymeric phase, a portion of the final polymericphase being intimately attached to at least one of the initial or secondpolymer phases.

According to another aspect of this invention, it is directed to acomposition used for damping which comprises: (a) soft crosslinkedelastomer containing (b) microscopically discrete segments of themulti-phase, thermoplastic elastomeric polymer disclosed above. Theelastomer is crosslinked with (d) curative in an amount sufficient tocrosslink the elastomer.

According to another aspect of the invention, it is directed to the useof such composition for damping purposes.

An object of the present invention is the use of a multi-phase polymerof certain morphology which exhibits excellent damping behavior over abroad temperature range.

Another object of this invention is the combination of these multi-phasepolymers as microscopically discrete segments with a thermosettable orvulcanizable elastomer or elastomer blend to yield a composition havingexcellent damping, good resistance to fatigue failure, and resistance tocreep. It is a further object to provide such compositions which arereadily processible and remoldable. It is a further object to provide adamping composition which provides outstanding damping performance overa wide range of use temperatures. It is a further object to provide suchcompositions as useful damping elements for vibration isolation incomputers, motors, automotive and truck components, such as steeringcolumn connectors, power generators, or rubber sheeting for vibrationisolation of computers, audio equipment, and the like.

These objects and others as will become apparent from the followingdisclosure are achieved by the present invention.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS

Damping is the absorption of mechanical energy by a material in contactwith the source of that energy. It is desirable to damp or mitigate thetransmission of mechanical energy from, e.g., a motor, engine, or powersource, to its surroundings. Elastomeric materials are often used forthis purpose. It is desirable that such materials be highly effective inconverting this mechanical energy into heat rather than transmitting itto the surroundings. It is further desirable that this damping orconversion is effective over a wide range of temperatures andfrequencies commonly found near motors, automobiles, trucks, trains,planes, and the like.

A convenient measure of damping is the determination of a parametercalled tan δ. A forced oscillation is applied to a material at frequencyf and the transmitted force and phase shift are measured. The phaseshift angle delta is recorded. The value of tan δ is proportional to theratio of (energy dissipated)/(energy stored). The measurement can bemade by any of several commercial testing devices, and may be made by asweep of frequencies at a fixed temperature, then repeating that sweepat several other temperatures, followed by the development of a mastercurve of tan δ vs. frequency by curve alignment. An alternate method isto measure tan δ at constant frequency (such as at 10 hz) over atemperature range.

We have defined a thermoplastic unfilled material as useful for dampingwhen tan δ>0.4 over at least a 4 decade range, preferably a 6 decaderange of frequency.

It is further important that this high degree of absorption of energy beaccompanied by good mechanical and thermal stability, as the partprepared from the subject polymers will be cycled through variousenvironments and repeatedly such to various forces of compression,tension, bending, and the like.

The thermoplastic elastomeric polymers described by Frankel et al, U.S.Ser. No. 683,902, filed 12/20/84, continuation application Ser. No.92,816 filed 9/3/87, are useful in the process and compositions of thisinvention. This reference is hereby expressly incorporated by referencesfor such teachings.

Also useful in the present invention are three-phase polymers in whichup to about 20% by weight of a third or of a final phase is polymerizedin the presence of two-phase polymers as described by Frankel et al. Thefinal polymeric thermoplastic phase is selected to have a glasstemperature greater than that of the initial polymeric phase, and aportion of the final polymeric phase will be intimately attached to theinitial and/or the second polymer phases.

The first phase polymer may contain small amounts, up to about 10%, ofcertain polar or functionalized monomers. Preferred are acids, such asacrylic, methacrylic, isoascorbic, maleic, fumaric, and the like ornitrile-containing monomers, such as acrylonitrile, methacrylonitrile,beta-cyanoethyl acrylate, and the like. Especially preferred is acrylicacid in amounts from about 2 to about 4 percent. Also especiallypreferred is acrylonitrile in amounts from about 2 to about 7 percent.

It is also preferred that the molecular weight of the first phase behigh. Use of mercaptan to lower molecular weight of the first phaseshould be avoided. Polymerization at low temperatures, such as belowabout 65°, is preferred.

It may be desirable to lower the glass temperature of the first phasepolymer. Such may be accomplished by lowering the amounts of lower alkylmethacrylate copolymerized or by use of an acrylate monomer with alonger side chain, such as 2-ethylhexyl acrylate. The third phasepolymers preferably contain mers which are predominately (meth)acrylicesters, and the hardness of the third phase may be controlled by thenature of the copolymer formed. It is preferred that the polymer beabout at least 50% lower alkyl methacrylate to about 100% lower alkylmethacrylate, the lower alkyl methacrylate being preferably methylmethacrylate, and from about 0 to about 50% of one or more lower alkylacrylates. Other monomers, such as styrene, other alkyl methacrylates,other alkyl acrylates, acrylonitrile, etc., may be present in amounts upto about 20%. Specific functionalized monomers, such as acrylic acid,methacrylic acid, acryloxypropionic acid, dimethylaminoethylmethacrylate, and the like, may be present in amounts up to about 5% ofthe third phase monomer mixture, as also may be monomers useful inpromoting adhesion to metal, wood, glass, or polymeric substrates, suchas those containing ureido or glycidyl functionality.

It is preferable that little or no new emulsifier be added during theformation of the third phase polymer. Initiators as taught in Frankel etal. may be utilized. It may be desirable to incorporate a chain transferagent with the third phase monomers. Preferred are primary, secondary ortertiary alkyl mercaptans, especially longer alkyl mercaptans, such asn-dodecyl or t-dodecyl. Other mercaptans, such as thioglycolate ormercaptopropionate esters, may be used, as may other well-known transferagents such as bromotrichloromethane. Such may be added directly withthe third phase monomers or separately before or during the third phasepolymerization.

The polymer emulsion may be agglomerated or aggregated by techniquesdescribed in the literature so as to increase the particle size. Suchagglomeration may be accomplished by pH adjustment, by partialcoagulation, and the like. Agglomeration may be accomplished prior to orafter final staging.

Particulate fillers such as carbon black, mica, talc, and the like maybe introduced into the multi-phase polymers at either theextrusion/isolation step or the isolated polymer may be re-processed toincorporate the filler, by means such as milling on a two-roll mill.Levels of filler may be as high as about 40%. Preferably suchparticulate fillers are reinforcing particulate fillers.

The multi-phase polymers may be converted into articles useful fordamping by known molding or extrusion techniques. Both injection moldingand compression molding may be employed. Useful articles include solidsupports, gaskets, bushings, interliners, and the like.

These multi-phase polymers are also described herein as thermoplasticelastomeric polymers, as they are both thermoplastic, in that they canbe molded and re-processed as true thermoplastics, yet exhibit anelastomeric response to stress, as well as the noted absorption ofmechanical energy.

In addition to their use in their own right as articles useful fordamping, the multi-phase polymers may be combined into thermosetelastomer(s) systems (i.e., elastomer, curative, fillers, etc.) toenhance damping performance thereof. The resulting thermosetcompositions are fatigue resistant and may be shaped during the curingprocess into useful articles, such as gaskets, motor mounts, bushings,sheets, and the like. Such compositions are especially useful in dampingvibration from motors, engines, and other mechanical components, as wellas vibrations resulting from vehicular or other motion in buildings,electronic and mechanical equipment, and the like. They are especiallyuseful in situations where heat and repeated vibration can cause fatigueimpairment of the long-term properties of other elastomer. The acrylicmulti-phase polymers are especially useful in their resistance to heatand oxidative degradation and oil swelling. Where heat resistance of thecomposition is desired, polymers of butadiene are preferably included inthe composition as a crosslinkable elastomer.

The thermoset elastomers may be based on any of a number ofcrosslinkable elastomers, such as polymers or copolymers of butadiene,ethylene-propylene-diene terpolymers, acrylic ester copolymerscontaining cure sites, polymers of isoprene, polymers of isobutylenecontaining unsaturation for curing, curable urethane elastomers,polymers from chloroprene monomer, and the like. Preferred arebromobutyl rubber, elastomeric polybutadiene, and polyisoprene;especially preferred are blends of natural or synthetic polymers ofisoprene with bromobutyl rubber in ratios of from about 10/90 to about90/10 parts by weight.

The Tabar et al. patents teach curatives, fillers, and the like andmethods for combining the materials of the crosslinkable elastomersystems, curing same, and physical testing thereof. These patents arehereby expressly incorporated by reference for such teachings. In thosepatents, strain crystallizable isobutylene polymers are taught assoftening materials when added in fatigue enhancing amounts. Theformulations and techniques for processing such systems are directlyapplicable to those used for the processing of composition comprisingcurable rubber with the thermoplastic multi-phase acrylic polymers ofthe present invention, except for the replacement of thepolyisobutylene. Thus, a preferred amount of thermoplastic multi-phasepolymer included in the natural rubber/bromobutyl rubber blends is fromabout 10 parts to about 40 parts per 100 parts of crosslinkableelastomer blend. An especially preferred amount is from about 10 to 30parts of multi-phase polymer per 100 parts of crosslinkable elastomer.

The crosslinkable elastomer may preferably be crosslinked by a curativecomprising a curing agent selected from the group consisting of: a) asufficient amount of sulfur to provide an efficient or semi-efficientcrosslinking of the soft thermoset composition; b) isocyanate or blockedisocyanate in an amount sufficient to crosslink the elastomer. The useof sulfur is especially preferred.

EXAMPLES

The examples are intended to illustrate the present invention and not tolimit it except as it is limited by the claims. All temperatures are indegrees Celsius. All percentages are by weight unless otherwisespecified, and all reagents are of good commercial quality unlessotherwise specified.

Standard procedures are used to characterize the emulsions. Particlesizes are determined by a quasielastic light scattering technique usinga Nano-Sizer* particle size analyzer manufactured by Coulter ElectronicsInc. The procedures used to determine soluble fraction and gel swellratio as given below.

The soluble fraction and gel swell ratio are polymer characteristicswhich are determined using acetone as the solvent. A known weight ofpolymer (either as the emulsion or as the isolated polymer) is placed ina centrifuge tube along with about 50 times the polymer weight ofacetone (e.g., 0.5 g of polymer in 25 g acetone in a 50 ml. tube). Aftershaking, usually overnight, the sample is centrifuged (20,000 rpm for60-90 min.) to precipitate the insoluble gel. The clear supernate isremoved and dried to determine soluble polymer. The gel is redispersedin acetone for at least 4-6 hours and centrifuged again. The clearsupernate is removed and dried as before. If the second extraction givesmore than about 5% soluble fraction, the extraction is repeated untilless than about 5% is found in the supernate. The weights of the polymerin the soluble fractions are summed and the percent soluble fraction iscalculated as (weight of soluble polymer/total polymer weight)×100.

After the last extraction, the weight of the acetone swollen gel isdetermined and the gel swell ratio calculated as weight of wet geldivided by (total polymer weight-soluble polymer weight).

All milling and molding for Examples 1-6 were performed at 177° C. Thetensile and elongation measurements were performed according toASTM-D-882; the Tg measurements according to ASTM-D-3418-75 on aPerkin-Elmer DSC-2.

The following abbreviations are used in certain portions of theexamples: BA=butyl acrylate; EA=ethyl acrylate; AA=acrylic acid;MAA=methacrylic acid; AN=acrylonitrile; MMA=methyl methacrylate;BGDMA=1,3-butyleneglycol dimethacrylate; BMA=butyl methacrylate;IM=polyisobutylene; St=styrene; BR=elastomeric poly(butadiene);NR=natural rubber.

EXAMPLE 1 Preparation of a two-phase polymer with five parts of a secondcross-linked phase

A monomer emulsion was prepared of the following ingredients:

    ______________________________________                                        Water               435 g                                                     Sodium lauryl sulfate (28%)                                                                       27.7 g                                                    Butyl acrylate      1353.7 g                                                  Acrylonitrile       103.8 g                                                   Methacrylic acid    24.5 g                                                    ______________________________________                                    

This emulsion was added in 5 shots to a vessel containing 645 g waterand was conducted at 50° C. and polymerized using a redox systemconsisting of 2.28 g cumene hydroperoxide and 1.54 g sodium sulfoxylateformaldehyde. After completion of the reaction, 78 g of butyleneglycoldimethacrylate was added and polymerized with 1.0 g t-butylhydroperoxideand 0.5 g isoascorbic acid. A sample of the emulsion was precipitatedvia freezing. The dried sample was milled and pressed into a 1/8" sheet.Other characteristics of the polymer are presented in Example 2.

EXAMPLE 2 Preparation of a three-phase polymer with 15 parts of a hardouter phase (Tg of final phase ca. 57° C.)

An emulsion was prepared in the same manner as in Example 1 except thata third phase was added in a one-shot mode consisting of 220.2 g methylmethacrylate and 55.1 g butyl acrylate and polymerized with 0.23 gsodium persulfate and 0.23 g sodium formaldehyde sulfoxylate. Theprecipitated and dried resin was milled and molded as in Expl. 1. Thefollowing physical properties were obtained:

    ______________________________________                                        Tensile Max.       Elong. at break                                                                           Tg                                             kg/cm.sup.2        %           °C.                                     ______________________________________                                        Expl. 1 11.3           312         -26                                        Expl. 2 46.6           720         -24                                        ______________________________________                                    

An Instron Tensile Tester was used to measure free-film mechanicalproperties. Films were cast in polypropylene petri dishes and allowed todry at least two weeks. The film thickness was 0.09-0.1 cm. If required,films were frozen to separate from the dish and/or talc was applied tofacilitate handling. A die was used to cut a dog-bone shaped samplehaving 0.64 cm width in the thin area. The ends were wrapped withmasking tape before being clamped in the Instron jaws.

The following parameters were used in the Instron tester

    ______________________________________                                        Crosshead speed:     2.54 cm/min.                                             Initial gap:         1.27 cm                                                  ______________________________________                                    

In general, samples were run in duplicate.

Data reported are:

    ______________________________________                                        Tensile (max.)                                                                            the highest strength observed                                     Tensile (break)                                                                           the tensile strength when the sample breaks                       Elongation (max.)                                                                         the elongation at tensile maximum                                 Elongation (break)                                                                        the elongation when the sample breaks                             ______________________________________                                    

EXAMPLE 3 A two-phase all-acrylic polymer with five parts of a highlycrosslinked second phase

Examples 3 and 4 demonstrate that the presence of a hard thermoplasticouter phase allows achievement of acceptable tensile properties with afirst phase having a lower glass temperature. A 5-gallon reactor wascharged with 8000 g water and heated to 55° C. A monomer emulsion wasprepared in another vessel consisting of: 2250 g water, 390 g SiponateDS-4, 1596 g butyl acrylate, 7286.5 g butyl methacrylate and 142.5 gmethacrylic acid. A seed was prepared in situ by adding 583 g of themonomer emulsion and initiating it with 5 g of a 1% aqueous solution offerrous sulfate, followed by 100 g of a solution of 18 g sodiumpersulfate in 500 g water and 100 g of a solution of 15 g sodiumbisulfite in 500 g water. After the exotherm, the remaining monomeremulsion was added gradually over ca. 2.5 hours together with theremaining solutions of the persulfate and bisulfite maintaining thereaction temperature at 65°±3° C. A 30 min. hold followed the end offeeds, after which the reaction was cooled to 45° C. and 475 g ofbutyleneglycol dimethacrylate was added followed by solutions of 3.4 gt-butylhydroperoxide in 50 g water and of 2.5 g isoascorbic acid in 50water. The reaction was held for 20 minutes after the reaction reachedits peak. A sample was precipitated by freezing, washed and dried. Thecalculated Tg of the first-phase polymer was +1° C.

EXAMPLE 4 A three-phase all-acrylic polymer with 15 parts of a hardouter phase

A 5-gallon vessel was charged with 8000 g water and thoroughlydeaerated. A monomer emulsion was prepared consisting of 2000 g water,351.1 g Siponate DS-4, 2422.5 g butyl acrylate, 5531.4 g butylmethacrylate and 121.1 g methacrylic acid. The vessel was heated to 55°C. and a seed was prepared in situ by adding 520 g monomer emulsion andinitiating it with 100 g of a solution of 16.15 g of sodium persulfatein 500 g water followed by 100 g of a solution of 13.75 g sodiumbisulfite in 500 g water and 5 g of a 1% aqueous of ferrous sulfate.After the exotherm, the remaining monomer emulsion was added graduallyover 2 hours together with the remaining solutions of sodium persulfateand sodium bisulfite. The reaction temperature was maintained at 65°±2°C. A hold period of 30 min. followed the end of the feeds after whichthe reaction was cooled to 45° C., 425 g of butyleneglycoldimethacrylate was added and initiated with solutions of 3 gt-butylhydroperoxide in 50 g water and 2.5 g isoascorbic acid in 50 gwater. The reaction was kept for 30 minutes after which 1200 g methylmethacrylate and 300 g butyl acrylate was added and initiated withsolutions of 1.5 g sodium persulfate in 75 g water and of 1.25 g sodiumformaldehyde sulfoxylate in 75 g water. After a hold of 30 minutes, asample was precipitated by freezing, washed and dried. The glasstemperature of the first-phase polymer was calculated as -9° C. It wasnoted that films from polymers containing butyl methacrylate in thefirst phase were less prone to exhibit whitening on exposure to water attemperatures of 70° C. or above.

The samples of Examples 3 & 4 were milled and molded into 1/8" sheetsand the following physical properties were obtained:

    ______________________________________                                                Tensile   Elong. at Break                                                                           Tg                                                      kg/cm.sup.2                                                                             %           °C.                                      ______________________________________                                        Example 3 91.0        325         18                                          Example 4 85.2        318          6                                          ______________________________________                                    

EXAMPLE 5 The use of the third phase allows one to improve both tensilestrength and lower the glass temperature of the multi-phased polymer

A monomer emulsion was prepared consisting of 2241 g water, 64.8 gSiponate DS-10, 5265 g butyl acrylate, 2673 g methyl methacrylate and162 g of methacrylic acid. A reaction vessel containing 6840 g water wasdeaerated and a solution of 16.2 g Siponate DS-10 in 54 g water wasadded. The vessel was heated to 55° C., 728 g of the monomer emulsionprepared above was placed in the reactor and initiated with 90 g of asolution of 16.2 g sodium persulfate in 630 g water, 90 g of a solutionof 13.5 g sodium bisulfite in 630 g water and 13 g of a 1% aqueoussolution of ferrous sulfate. After the exotherm, the remaining monomeremulsion was added gradually over a 3 hours period together with theremaining solutions of sodium persulfate and sodium bisulfitemaintaining the reaction temperature at 65°±2° C. A 1/2 hour holdfollowed the end of feeds after which the reactor was cooled to 45° C.,426 g of butyleneglycol dimethacrylate was added and initiated withsolutions of 3 g t-butylhydroperoxide in 45 g water and of 2.2 gisoascorbic acid in 45 g water. After a 1/2 hour hold, the reaction wascooled. A sample was precipitated by freezing, washed and dried.

EXAMPLE 6

A monomer emulsion was prepared consisting of 2000 g water, 351 gSiponate DS-4, 5650 g butyl acrylate, 2301 g methyl methacrylate and 121g methacrylic acid. A reaction vessel containing 8000 g water wasdeaerated with a nitrogen sparge, heated to 55° C. and 520 g of theprepared monomer emulsion was added. It was initiated with 100 gsolutions of each, 16.2 g sodium persulfate in 500 g water, 13.7 gsodium bisulfite in 500 g water and with 5 g of a 1% aqueous solution offerrous sulfate. After the exotherm, the remaining monomer emulsion,persulfate and bisulfite solutions were added gradually over a 2.5 hoursperiod maintaining a reaction temperature of 65°±2° C. A 1/2 hour holdfollowed the end of the feeds. The reaction was cooled to 45° C., 425 gof butyleneglycol dimethacrylate was added and initiated with solutionsof 3 g t-butylhydroperoxide in 50 g water and of 2.2 g isoascorbic acidin 50 g water. After a hold of 30 minutes, 1200 g methyl methacrylateand 300 g butyl acrylate was added and initiated with aqueous solutionsof 1.5 g sodium persulfate and of 1.25 g sodium formaldehydesulfoxylate. After 30 minutes, the reaction was cooled, a sample wasprecipitated by freezing, washed and dried. The samples of examples 5 &6 were milled and molded and the following physical properties wereobtained:

    ______________________________________                                        Tensile, g/cm.sup.2                                                                            Elong. at break, %                                                                          Tg, °C.                                 ______________________________________                                        Example 5                                                                             54.5         535            4                                         Example 6                                                                             82.3         450           -3                                         ______________________________________                                    

EXAMPLE 7

The procedure of Example 1 was followed to prepare an emulsion of butylacrylate/acrylonitrile/acrylic acid=91.6/7/1.4. The reaction wasconcluded prior to the addition of any crosslinking monomer. Theparticle size in Examples 7-10 was set by the addition to the initialaqueous phase of 64 g of a 45% solids seed polymer; said seed polymerwas approximately methyl methacrylate/butyl acrylate/methacrylic acid49/50/1 and of particle size ca. 100 nanometers.

EXAMPLE 8

The procedure of Example 1 was followed to prepare a two-phase polymerof butyl acrylate/acrylonitrile/acrylic acid//butylene glycoldimethacrylate=97(91.6/7/1.4)//3.

EXAMPLE 9

The emulsion of Example 7 (400 parts, 59.7% solids) was further reactedby addition of a monomer emulsion of:

    ______________________________________                                                           Parts                                                      ______________________________________                                        Butyl acrylate       21.1                                                     Methyl methacrylate  20                                                       Methacrylic acid     1.05                                                     Siponate DS-4 anionic surfactant                                                                   0.19                                                     Water                10                                                       ______________________________________                                    

at 50° C., followed by addition of 0.055 parts of t-butyl hydroperoxideand 0.036 parts of isoascorbic acid (as 5% aqueous solutions). Thereaction exothermed to 59° C. A second addition of similar amounts ofinitiator was made in 15 minutes. The resulting solids content was60.3%. The calculated glass temperature of the outer phase was +4° C.and of the first phase was -47° C.

EXAMPLE 10

The latex of Example 8 (391.5 grams at 61% solids) was treated with theouter phase monomer mix in the proportions and amounts of Example 9 toform a three-phase polymer.

EXAMPLE 11

This example compares the properties of the polymers of Examples 7 to 10to illustrate the improved balance of properties imparted by the finalharder phase. Values of tensile strength and elongation were measured atroom temperature.

    ______________________________________                                                      phase   Soluble       Tensile                                                                              Elon-                              Ex-   phase   III,    Fraction                                                                             Swelling                                                                             Strength                                                                             gation                             ample II, %   %       (%)    Ratio  (kg/cm.sup.2)                                                                        (%)                                ______________________________________                                        7     0        0      93     a      1.5    1717                               8     3        0      37     22     5.9     910                               9     0       15      75     67     13.6   1882                               10    3       15      34     20     26.7   1200                               ______________________________________                                         a = Too lightly crosslinked to measure                                   

EXAMPLE 12 Three-phase polymer useful for damping in blends with athermosettable rubber

The process of Example 2 was used, except that the ratio of monomers wasaltered slightly to produce a multi-phase polymer of Phase I//PhaseII/Phase III=79.3//4.2//15, wherein Phase I isBA/AN/St/MAA=90.8/7.0/0.6/1.6; Phase II is BGDMA 100; Phase III isMMA/BA=80/20. A small amount of a polymer seed of ca. 80 nm size,composition BA/MMA/AA=49.5/49.5/1, was added prior to the initialpolymerization. The resulting latex was coagulated by the techniquestaught by Frankel et al cited herein of single-unit coagulation, liquiddewatering, and extrusion, and extruded into 3 mm pellets. Similarresults will be obtained if the polymer is coagulated by freezing,washing the gumstock with water, squeezing the gumstock free of water,and drying in vacuo, as the subsequent compounding does not require thethermoplastic elastomeric polymer to be in pellet form.

EXAMPLE 13

This example illustrates the preparation of a three-phase polymer basedon a polymer of somewhat higher glass temperature, wherein no seed wasemployed. The process of Example 2 was used, except that the ratio ofmonomers was altered slightly to produce a polymer of Phase I//PhaseII/Phase III=80.8//4.2//15, wherein Phase I is BA/BMA/MAA=30.0/68.5/1.5;Phase II is BGDMA 100; Phase III is MMA/BA=80/20. The polymer wasisolated as in Example 12.

EXAMPLE 14

This example illustrates a polymer similar to that of Example 4 butwithout a third thermoplastic phase. The process of Example 4 wasfollowed, except the step of polymerizing the third phase was omitted.The polymer was isolated by the method of Example 12. The polymer has aweight ratio of Phase I//Phase II of 95//5; Phase I isBA/BMA/MAA=17.7/80.7/1.6; Phase II is BGDMA 100.

EXAMPLE 15

This example illustrates the preparation of a two-phase polymer of Tgca. 25° C. The process of Example 4 was followed, except the step ofpolymerizing the third phase was omitted. The polymer was isolated bythe method of Example 12. The polymer has a weight ratio of PhaseI//Phase II of 95//5; Phase I is BA/MMA/MAA=50.0/48.5/1.5; Phase II isBGDMA 100.

EXAMPLE 16

The process of Example 15 was repeated to yield a two-phase polymer ofTg ca. 0° C. The polymer has a weight ratio of Phase I//Phase II of95//5; Phase I is BA/MMA/MAA=65.0/33.0/2.0; Phase II is BGDMA 100.

EXAMPLE 17

This example illustrates the damping properties of the two- andthree-phase polymers of the previous examples. Materials from certain ofthe above preparations after isolation by either precipitation orextruder coagulation were processed into appropriate test specimens bypressing in a Carver press between Mylar polyester spacers at 180° C.platen temperature for 2 to 3 minutes at 1.38×10⁹ dynes/square cm(piston pressure), then cooling to 15° C. and pressing for 4 to 5minutes at 6.9×10⁸ dynes/square cm (piston pressure). Spacer plates wereused to obtain thicknesses of 3.175 mm for dynamic mechanical testing or0.51 mm for tensile and elongation testing. Room temperature tensileproperties were determined to show that acceptable strength andelongation were obtained, and that the degree of tension set or physicalrecovery was not excessive. The glass temperature was determined bydifferential scanning calorimetry.

The dynamic mechanical values are measured on a Rheometrics DynamicSpectrometer (Rheometrics Instruments, Piscataway, N.J.), equipped withrectangular tooling torsion fixtures. Samples of the acrylic two- orthree-phase polymer are compression molded and cut into strips of 63.5mm length by 12.7 mm wide by 3.2 mm thickness. The sample is driedovernight at 60° C. in vacuo, and then affixed to the jaws of thespectrometer. The sample is cooled to -140° C. A maximum strain of only0.4% is utilized until the test temperature is above that of the onsetof rubbery properties; at no time does the maximum strain exceed 10%.Measurements are made at 20° C. intervals over a frequency sweep of 0.1to 200 radians/second. The maximum temperature may be as high as 140° C.but usually these polymers begin to exhibit obvious viscous flow at thehighest temperature and the geometry is not maintained.

The plots obtained of tan δ vs. frequency at each temperature are thensuperimposed, utilizing the Williams-Landel-Ferry equation (J. D. Ferry,Viscoelastic Properties of Polymers, Chapter 13, John Wiley and Sons,New York, 3rd edition, 1980). From the master plot of tan δ vs. logfrequency is determined the frequency range in decades over which tan δexceeds 0.4.

    ______________________________________                                                                Tensile                                               Polymer                                                                              Tg,    Strength, Elongation,                                                                           Maximum Range,                                Example                                                                              °C.                                                                           kiloPascals                                                                             %       Tan δ                                                                           Decades                               ______________________________________                                        12     -20    6900      800     0.8     4                                     13      +5    7280      300     0.8     4                                     14     +20    9660      300     1.4     6                                     15     +25    13800     200     1.5     6                                     16       0    4800      500     1.4     6                                     ______________________________________                                    

EXAMPLE 18

This example illustrates the excellent damping behavior and fatigue lifeof three compositions, A, B, and C, made according to the invention ascompared to those of a composition D, which was not made according tothe invention. Compositions A, B, and C comprise the two-phase acrylicthermoplastic elastomeric polymers from Examples 15, 16, and 14,respectively, incorporated in the thermosettable elastomer formulationshown below. In these formulations, the two-phase acrylic thermoplasticelastomeric polymers above were used as the additive polymer and X=60.The reference composition D incorporates polyisobutylene (IM) as theadditive polymer and X=20. Phr=parts per hundred of cross-linkableelastomer.

                  TABLE 18-1                                                      ______________________________________                                        Composition Formulation                                                       Material              phrNR                                                   ______________________________________                                        SMR-L (Natural Rubber)                                                                              X                                                       Bromobutyl Rubber     100-X                                                   Additive Polymer      20                                                      Carbon Black          35                                                      (N-660)                                                                       Stearic Acid          2                                                       Zinc Oxide            5                                                       Parraffinic Petroleum Oil                                                                           5                                                       ASTM Type 104B                                                                Diphenylamine Derivative                                                                            1.5                                                     2- and 3- Methyl      1.5                                                     Mercaptobenzimidazole                                                         Thiocarbamyl Sulfenamide                                                                            1.20                                                    N-Oxydiethylene Benzothiazole                                                                       .55                                                     2-Sulfenamide                                                                 Elemental Sulfur      0.40                                                    ______________________________________                                    

The first three ingredients (the polymeric components) were combined andmixed in a laboratory-size (model BR) Banbury mixer for 1.5 minutes. Theremaining ingredients exclusive of accelerators and sulfur were added intwo portions and the mixture masticated for a total of 6.0 minutes. Itwas then dumped from the Banbury, sheeted with a rubber mill, andallowed to cool. Curatives (accelerators and sulfur) were subsequentlyadded to 550 g. of the mixture on a rubber mill according to ASTM D3182,with no pre-conditioning of the carbon black.

The materials were molded according to ASTM D3182 and cured to 100%optimum as determined by Monsanto oscillating disc rheometer. Curetemperatures were varied for different moldings of the same formulationto optimize fatigue properties. The cure temperatures listed in Table 1were optimal for each formulation.

Ultimate tensile strength and elongation at break were determined underambient conditions according to ASTM D412 (die C) and tear strengthaccording to ASTM D624 (die B). An electromechanical tester was used ata test speed of 500 mm per minute.

Compression set testing was done according to ASTM D395 (method B). Thetest specimens were held under 25% compression for 22 hours at 125° C.in ventilated, air-circulating oven, and a 30 minute relaxation at roomtemperature was allowed before taking final measurements. Testing formechanical fatigue was conducted either as taught by Tabar (more fullydescribed by Lemieux et al.), or by test method ASTM D4482-85 using aMonsanto fatigue-to-failure tester.

Dynamic-mechanical properties including tan δ and glass transitiontemperature (Tg) were determined on a Polymer Laboratories DMTA.Isochronal (10 Hz) data was collected in simple tension from -100° to100° C., at a strain displacement of 62 microns, and a heating rate of2° C./minute. Isothermal data was collected on simple shear specimensover frequencies of 0.01-100 Hz at 20° C. intervals from -20° to 100° C.

                  TABLE 18-2                                                      ______________________________________                                        Composition                                                                             Additive Polymer                                                                           Cure Temperature, °C.                           ______________________________________                                        A         Example 15   140                                                    B         Example 16   140                                                    C         Example 14   140                                                    D         IM           170                                                    ______________________________________                                    

The compositions containing the two-phase acrylic thermoplasticelastomers have comparable or improved fatigue resistance compared tothe reference composition containing polyisobutylene. The comparison oflog (fatigue life), as cycles, against log (strain energy) (mJ/mm³) wasplotted, and the numbers in Table 18-3 were derived using linearregression. All three of the compositions according to this invention(A, B, and C) have improved fatigue resistance over the referencecomposition (D) at test energies up to 630 mJ/mm³. The compositioncontaining the additive polymer from Example 16 had the best fatiguelife over the entire range of the test.

                  TABLE 18-3                                                      ______________________________________                                        Fatigue Resistance of Blends A, B, C, and D                                   Strain Energy                                                                             Log Fatigue Life, cycles                                          mJ/mm.sup.3 A      B          C    D                                          ______________________________________                                         400        --     5.75       5.63 5.56                                        600        5.75   5.46       5.31 5.30                                        700        5.40   5.35       5.19 5.21                                       1000        5.26   5.10       4.91 4.98                                       1150        4.83   5.00       4.80 4.89                                       1400        4.67   4.86       4.65 4.77                                       ______________________________________                                    

The isochronal (10 Hz) tan δ/temperature response for these compositionsare presented in Table 18-4. All three compositions according to theinvention display more uniform damping behavior over the temperaturerange of -50° to -20° C. as compared to that of the referencecomposition. Also, the same three formulations, A, B, and C, providemuch improved damping behavior over that of the reference composition inthe temperature range from 0° to 20° C., especially so for formulationsB and C.

                  TABLE 18-4                                                      ______________________________________                                        Isochronal Damping Response for                                               Compositions A, B, C, and D                                                              tan δ for Compositions                                       Temperature, °C.                                                                    A      B          C    D                                         ______________________________________                                        -55          0.28   0.24       0.43 0.46                                      -50          0.55   0.52       0.63 0.92                                      -40          0.83   0.69       0.64 0.97                                      -20          0.71   0.57       0.53 0.69                                        0          0.31   0.32       0.30 0.30                                      +20          0.17   0.30       0.29 0.14                                      ______________________________________                                    

This improved damping behavior was confirmed using ambient response ofthe formulations. Table 18-5 is taken from the experimental plot of tanδ/log frequency (Hz).

                  TABLE 18-5                                                      ______________________________________                                        Damping Response for Compositions A, B, C, and D                              at Various frequencies at T = 20° C.                                             tan δ for Compositions                                        Frequency, Hz                                                                             A      B          C    D                                          ______________________________________                                        0.01        0.15   0.12       0.16 0.08                                       0.10        0.11   0.15       0.18 0.07                                       1.0         0.10   0.17       0.18 0.08                                       10.0        0.16   0.21       0.22 0.14                                       50.0        0.28   0.31       0.29 0.26                                       ______________________________________                                    

It was also found that inclusion of the multi-phase acrylic elastomersin the compositions imparts higher values of tan δ over a wide range oftest frequencies. At 80° C. similar behavior is observed, except at thevery low frequencies where tan δ is nearly the same for allformulations.

                  TABLE 18-6                                                      ______________________________________                                        Damping Response for Compositions A, B, C, and D                              at Various Frequencies at T = 80° C.                                             tan δ for Compositions                                        Frequency, Hz                                                                             A      B          C    D                                          ______________________________________                                        0.10        0.09   0.10       0.09 0.08                                       1.0         0.09   0.10       0.09 0.07                                       10.0        0.11   0.10       0.11 0.07                                       50.0        0.16   0.12       0.15 0.09                                       100.0       0.19   0.15       0.19 0.11                                       ______________________________________                                    

Table 18-7 is a comparison of the physical properties of thecompositions. The effect of varying the additive polymer is negligible,except for a slight lowering of the tensile strength for Sample A and aslight improvement in compression set for Sample C.

                  TABLE 18-7                                                      ______________________________________                                        Physical Property Comparison                                                         Tensile Elongation Tear   % Compression                                Sample (MPa)   %          Strength                                                                             Set                                          ______________________________________                                        A      15.0    548        53.1   36.5                                         B      17.4    598        56.4   34.6                                         C      17.3    613        60.8   33.4                                         D      18.2    680        54.8   35.4                                         ______________________________________                                    

EXAMPLE 19

This example illustrates the excellent damping behavior and fatigue lifeof a composition E made according to the invention as compared to thatof composition D, the reference composition made in Example 18.Composition E comprises the three-phase acrylic thermoplastic elastomerfrom Example 12 in the thermosettable elastomer formulation shown inExample 18. The three-phase acrylic polymer was incorporated as theadditive polymer with X=60. Sample E was mixed and molded according tothe procedure of Example 18 and cured at a cure temperature of 170° C. Acomparison of the isochronal tan δ behavior for the two formulations isshown below. As can be seen from these data, composition E whichcomprises the three-phase acrylic polymer displayed a more uniformdamping response as compared to that of reference composition D over thetemperature range of -50° to -20° C., and surpassed the damping ofreference composition D over the range of -15° to 20° C.

                  TABLE 19-1                                                      ______________________________________                                        Isochronal Damping Response for Compositions D and E                                         tan δ for Compositions                                   Temperature °C.                                                                         D      E                                                     ______________________________________                                        -55              0.46   0.40                                                  -50              0.92   0.66                                                  -40              0.97   0.68                                                  -20              0.69   0.56                                                    0              0.30   0.37                                                  +20              0.14   0.17                                                  ______________________________________                                    

EXAMPLE 20

This example illustrates the expected excellent physical properties of acomposition according to this invention. The composition is madeaccording to the formulation and procedure of Example 18 except that thebromobutyl rubber is replaced by 25 phr of polybutadiene rubber (BR).This composition includes a multi-phase acrylic thermoplastic elastomer,such as taught in Example 16. The heat-aged physical properties of thisformulation would be expected to be superior to those of typical NRdamping materials due to the inclusion of the polybutadiene rubber inthe composition. Tabar et al in U.S. Pat. No. 4,362,840 disclosed theimprovement of heat aging properties afforded elastomeric compositionsof NR, BR and IM. The improved damping behavior of examples 18 and 19over formulations containing IM is fully expected to be analogous tothis example, and should provide an advantage in applications wherehigher heat resistance is necessary. Due to the thermoplastic nature ofthe multi-phase acrylic polymers, and therefore the lower viscosityrelative to most elastomers under high-shear mixing temperatures, thefatigue-resistance-enhancing discrete particle morphology will bepresent in this formulation.

EXAMPLE 21

This example makes a direct comparison between a composition utilizing amulti-phase acrylic elastomer as the additive polymer and acompositionally analogous formulation utilizing IM as the additivepolymer. Sample B, previously described, was used as the compositioncontaining the multi-phase acrylic elastomer. Sample F was prepared withIM as the additive polymer in the formulation of Example 18-1 with X=40and Y=20, and cured at 170° C.

Dynamic measurements were taken with a Rheometrics RMS 800 mechanicalspectrometer at 25° C. and 100° C. using the parallel plate geometry.Data was collected and recorded at rates from 1 to 100 radians/sec., andthe samples were placed under 15% compression to prevent slipping.

Values from the plotted data are shown in Table 21-1. Sample B exhibitsan improved tan δ response over the entire range of frequencies incomparison with the prior art sample, and the trend is maintained athigh temperature.

                  TABLE 21-1                                                      ______________________________________                                        Comparison of Damping Behavior of Composition                                 Containing Multi-Phase Acrylic Polymer with One                               Containing Isobutylene Polymer                                                Rate of    Damping (tan δ) of                                           Measurement,                                                                             Formulated/Cured Compounds                                         radians/sec.                                                                             B, 25°                                                                         F, 25°                                                                            B, 100°                                                                      F, 100°                            ______________________________________                                        1          0.22    0.21       0.14  0.14                                      6          0.26    0.22       0.15  0.13                                      10         0.27    0.22       0.15  0.13                                      22.5       0.31    0.24       0.15  0.12                                      40         0.33    0.25       0.15  0.12                                      60         0.36    0.27       0.15  0.12                                      100        0.39    0.30       0.15  0.12                                      ______________________________________                                    

While the invention has been described with reference to specificexamples and applications, other modifications and uses for theinvention will be apparent to those skilled in the art without departingfrom the spirit and scope of the invention defined in the appendedclaims.

We claim:
 1. A process for damping comprising:a) preparing in emulsion amulti-phase, thermoplastic elastomeric polymer having at least twopolymeric phases comprising:i) an initial linear or lightly crosslinkedpolymeric phase polymerized from an alpha,beta-ethylenically unsaturatedmonomer, wherein said alpha, beta-ethylenically unsaturated monomercomprises from 0 to about two percent by weight of multi-ethylenicallyunsaturated monomer, ii) a second polymeric phase in the form ofdiscrete domains of about 2 to about 50 nanometers in diameter dispersedwithin said initial polymeric phase, wherein said second polymeric phaseis polymerized from at least one ethylenically unsaturated monomercomprised of about 5 percent to 100 percent by weight multifunctionalmonomer having at least two sites of ethylenic unsaturation, wherein theweight ratio of said second polymeric phase to said initial polymericphase plus said second polymeric phase is from about 1:100 to about 1:2;b) isolating said multi-phase polymer in solid form; c) processing saidsolid multi-phase polymer into a shaped object; d) placing said shapedobject between two surfaces, at least one of which is subject tovibrations, and damping said vibrations.
 2. The process of claim 1,wherein said multi-phase thermoplastic elastomeric polymer furthercomprises a final polymeric thermoplastic phase whose glass temperatureis greater than that of said initial polymeric phase, a portion of saidfinal polymeric phase being intimately attached to at least one of saidinitial and said second polymer phases, and the weight ratio of saidfinal polymeric phase to said initial polymeric phase plus said secondpolymeric phase plus said final polymeric phase is up to about 1:5.
 3. Aprocess for damping comprising:a) preparing in emulsion a multi-phase,thermoplastic elastomeric polymer having at least two polymeric phasescomprising:i) an initial linear or lightly crosslinked polymeric phasepolymerized from an alpha,beta-ethylenically unsaturated monomer,wherein said alpha, beta-ethylenically unsaturated monomer comprisesfrom 0 to about two percent by weight of multi-ethylenically unsaturatedmonomer, ii) a second polymeric phase in the form of discrete domains ofabout 2 to about 50 nanometers in diameter dispersed within said initialpolymeric phase, wherein said second polymeric phase is polymerized fromat least one ethylenically unsaturated monomer comprised of about 5percent to 100 percent by weight multifunctional monomer having at leasttwo sites of ethylenic unsaturation, wherein the weight ratio of saidsecond polymeric phase to said initial polymeric phase plus said secondpolymeric phase is from about 1:100 to about 1:2; b) isolating saidmulti-phase polymer in solid form; c) blending a particulate filler withsaid solid multi-phase polymer, the weight ratio of said filler to saidmulti-phase polymer plus said filler being up to about 1:2.5; d)processing said solid multi-phase polymer into a shaped object; e)placing said shaped object between two surfaces, at least one of whichis subject to vibrations, and damping said vibrations.
 4. The process ofclaim 3, wherein said multi-phase thermoplastic elastomeric polymerfurther comprises a final polymeric thermoplastic phase whose glasstemperature is greater than that of said initial polymeric phase, aportion of said final polymeric phase being intimately attached to atleast one of said initial and said second polymer phases, and the weightratio of said final polymeric phase to said initial polymeric phase plussaid second polymeric phase plus said final polymeric phase is up toabout 1:5.